Semiconductor laser distributed feedback laser including mode interrupt means

Abstract

A buried heterostructure type distributed feedback semiconductor laser comprises a semiconductor substrate transparent to an oscillation light beam, a laser stripe including a diffraction grating, an active layer, and a guiding layer formed on the semiconductor substrate, and semiconductor peripheral region formed so as to cover the laser stripe on the semiconductor substrate. The semiconductor peripheral region is transparent to an oscillation light beam. Rectangular grooves are formed near both sides of emission facet of the laser stripe more deeply than the laser stripe. Since a radiation mode from the laser stripe is reflected and scattered by the grooves, it cannot hardly reach the emission facet. Therefore, the radiation mode does not interfere with an output beam from the laser.

What is claimed is: 
     
       1. A semiconductor laser comprising: a semiconductor substrate transparent to an oscillation light beam;   a laser stripe through which an electric current flows, including an active laser, a guiding layer formed on said semiconductor substrate, and a diffraction grating formed along said guiding layer;   a phase shifted portion formed at a halfway point of said diffraction grating;   a semiconductor peripheral region formed so as to cover said laser stripe on said semiconductor substrate, said semiconductor peripheral region being transparent to an oscillation light beam; and   interrupting means for interrupting a radiation mode light beam radiated from said phase shifted portion to said semiconductor peripheral region, said interrupting means being located near both sides of the emission end of said laser stripe and in said semiconductor peripheral region so as not to interrupt an output light beam, and being formed by digging said semiconductor peripheral region and said semiconductor substrate to a greater depth than said laser stripe.   
     
     
       2. The semiconductor laser according to claim 1, wherein said interrupting means comprises rectangular grooves formed by digging said semiconductor peripheral region and said semiconductor substrate near both sides of the emission end of said laser stripe. 
     
     
       3. The semiconductor laser according to claim 2, wherein said grooves are arranged near both ends of said laser stripe. 
     
     
       4. The semiconductor laser according to claim 1, wherein said interrupting means comprises round holes formed by digging said semiconductor peripheral region and said semiconductor substrate near both sides of the emission end of said laser stripe. 
     
     
       5. The semiconductor laser according to claim 1, wherein said interrupting means comprises scoop regions formed by removing said semiconductor peripheral region and said semiconductor substrate on both sides of the emission end of said laser stripe. 
     
     
       6. The semiconductor laser according to claim 2, wherein said grooves are filled with a light absorbing material. 
     
     
       7. The semiconductor laser according to claim 4, wherein said holes are filled with a light absorbing material. 
     
     
       8. The semiconductor laser according to claim 1, wherein said interrupting means is located between said emission end and said phase shifted portion. 
     
     
       9. The semiconductor laser according to claim 1, wherein said semiconductor laser is a distributed feedback semiconductor laser for applying optical feedback by use of said diffraction grating. 
     
     
       10. The semiconductor laser according to claim 1, wherein both end of said laser stripe are cleavage facets aligned with cleavage facets of said semiconductor peripheral region and semiconductor substrate. 
     
     
       11. The semiconductor laser according to claim 10, wherein coats having a low reflectivity are provided on said cleavage facets.